Hoist with constant pressure one way brake

ABSTRACT

A low cost hoist operated by a motor on whose shaft is an overrunning clutch that rotates a load brake disc when the motor shaft rotates in load lowering direction, the disc engaging between a pair of brake plates acting with constant frictional pressure against opposed surfaces of the disc and enabling the hoist to support a load. Heat that is developed by slip friction will be divided between the brake plates when the motor operates to lower a load, and one of those plates is in heat conducting surface contact with the hoist frame, controlling temperatures due to the slip friction and reducing deterioration of the brake and hoist. The brake disc is formed by two disc portions in contact and mounted on the clutch through keying portions so staggered as to offer surfaces that locate the disc in a predetermined axial position on the clutch.

United States Patent Freeman 1111 3,825,100 [451 July 23, 1974 HOIST WITH CONSTANT PRESSURE ONE WAY BRAKE Inventor: Harvey Freeman, Brinkley, Ark.

Assignee: Eaton Corporation, Cleveland, Ohio Filed: June 14, 1972 Appl. No.: 262,909

US. Cl. 188/7l.2, 188/82.84, 188/218 XL, 192/12 B, 192/70.2, 192/7, 254/168 Int. Cl. F16d 67/02 Field of Search 188/71.2, 82.84, 218XL, 188/83; 192/3 R, 8 R, 12 B, 12 BA, 70.2, 7;

References Cited UNITED STATES PATENTS Schuetz mas/71.2

Christison 19213 R Primary ExamineF-Benjamin W. Wyche Attorney, Agent, or Firrn-Teagno & Toddy [5 7] ABSTRACT A low cost hoist operated by a motor on whose shaft is an overrunning clutch that rotates a load brake disc when the motor shaft rotates in load lowering direction, the disc'engaging between a pair of brake plates acting with constant frictional pressure against opposed surfaces of the disc and enabling the hoist to support a load. Heat that is developed by slip friction will be divided between the brake plates when the motor operates to; lower a load, and one of those plates is in heatconducting surface contact with the hoist frame, controlling temperatures due to the slip friction and reducing deterioration of the brake and hoist. The brake disc is formed by two disc portions in contact and mounted on the clutch through keying portions so staggered as to offer surfaces that locate the disc in a predetermined axial position on the clutch. I V

4 Claims, 5 Drawing Figures HOIST WITH CONSTANT PRESSURE ONE WAY BRAKE This invention relates to power operated hoists that have a load brake for controlling lowering movements of the hoist.

It already has been recognized that certain advantages can be achieved when designing a hoist in which there is a load brake whose parts engage under constant pressure. For example, the U.S. Pat. application ofClara A. Lytle, Ser. No. 222,068, filed Jan. 3 1, I972 and assigned to the owner of the present application, shows a hoist design that comprises a brake of that kind, enabling the hoist to offer satisfactory operation while adapted to be built for sale at a relatively low price. That brake needs no mechanism for changing the brake pressure, the brake yielding with slipfriction when the hoist operates to lower a load, and there being a simple overrunning clutch that frees the hoist from the braking effect when the hoist lifts a load. I have now conceived by my invention an improved'hoist design utilizing certain features of the Lytle hoist, and achieving extremely effective operation with very little need for repair or maintenance service over extended periods of time. 1

In my invention, a hoist will comprise a pair of opposed brake plates that are mounted in aligned relation to the axis of an operating shaft that is rotated by a hoist motor, and that acts through speed reduction gearing to apply high torque to a rotatable load shaft on the hoist,the operating shaft being reversible in operation whereby to rotate the load shaft in load lifting-and load lowering directions. These brake plates are secured against rotationrelatively to the hoist frame, and are spring pressed so as to apply constant braking pressure against opposed surfaces of a friction brake disc between the plates. An overrunning clutch on the operating shaft rotates the brake disc in slip friction relation to the pair of brake plates when the shaft rotates in load lowering direction, each of those plates. accepting a portion of the frictional energy that is due to the relatively high speed of the operating shaft.

More particularly, I mount one of the brake plates in heat conducting surface contact with an end wall of the hoist frame, while the other of those plates has a surface that may be exposed to air. Thus, as a feature of my invention, I divide between two brake plates the heat that is developed by the slip friction of a brake disc rotating while under constant pressure by the plates, and l dissipate through the plates an amount of heat that will permit the brake temperature to remain with an acceptable range. Thereby I greatly. reduce or eliminate the detrimental effects that are due to the heat developed in a hoist that has a brake engaging with constant pressure.

As a detailed feature, I may mount the brake disc through keying portions so formed as toact also for holding the disc in a predetermined axial'position on the operating shaft. More particularly, I may assemble a plurality of disc portions in contact with one another to form the brake disc, the keying portions then being formed in a staggered relation so as to engage an opening in each disc portion while also engaging a contacting surface of an opposed disc portion.

stood, and in order that my contribution to the art may be better appreciated. Thereare, of course, additional features of my invention thatwill be described hereinafter and which will form thesubject of the claims appended hereto. Those skilled in the art will appreciate that the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out theseveral purposes of my invention. It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of my invention,in order to prevent the appropriation of my invention by those skilled in the art.

In the drawing:

FIG. 1 shows a longitudinal section of a hoist utilizing my invention;

FIG. 2 shows an end view of the hoist brake and clutch assembly;

FIG. 3 shows a section on the line 3-3 in FIG. 2, and further showing parts of the hoist;

FIG. 4 shows a section on the line 44 in FIG. 3; and

FIG. 5 shows an exploded perspective view of parts of the clutch and brake assembly.

Referring now more particularly to FIG. 1 of the drawing, I show a hoist H in which a clutch and brake assembly, indicated generally by the numeral 10, forms a part of the operating mechanism of the" hoist. The hoist mechanism further comprises a reversible motor M whose'shaft is connected through speed reduction gearing 11 to a load shaft'l2 that rotates to lift and to lower a load, the clutch and brake assembly 10 being connected to an end portion 13 of the motor shaft that extends outwardly through an opening in an end wall 14 on the hoist frame. I believe'that further details of the hoist motor and gearing will be unnecessary to an understanding of my present invention, and it is merely important to know here that the shaft of motor M will coact with the assembly 10 while rotating at a high speed relatively to the load shaft 12 whereby to effect lifting and lowering of a load.

As is best shown in FIGS. 3 and 4, the assembly 10 includes anoverrunning clutch 15 having a bushing 16 that is splined as at 17 to the end portion 13 of the 7 motor shaft. A clutch housing 18 is mounted through two series of roller bearings 19, 20 to rotate on the bushing 16, and a medial series of clutch rollers 21 is assembled between housing 18 and ramp surfaces 22 on the bushing 16. Persons who are skilled in the art will recognize that the rollers 21 and ramp surfaces 22- will act in a manner that is usual in overrunning clutches, but it should be understood here that the direction in which rollers 21 will act to lock bushing 16 to housing 18 will be the load lowering direction in which shaft 13 rotates, the rollers 21 effecting release when shaft 13 rotates in load lifting direction.

A pair of hub portions 23, 24 is mounted on the clutch housing 18 so as to form in effect an integral part of the housing, as by a press fit on the housing surface. The hub portions 23, 24 are complementary in shape and lprefe'r that they be identical, as best seen in FIG. 5. Thus, each hub portion 23, 24 has a circular part 25 adapted to be pressed onto the clutch housing 18, one

I have thus outlined ratherbroadly the more impor-' tant features of my invention in order that the detailed description thereof that follows may be better underend of each part 25 having a flange 26 or 26a whose another, but in relatively rotated positions that stagger the flanges 26, 26a so that their outlines are angularly relatedflas is most clearly indicated by full lines and phantom lines in FIG. 4. Y The hexagonal hub flanges 26, 26a in effect for keying portions that will engage openings in a pair of brake disc portions 28, 28a whereby to mount the disc portions to rotate integrally with the clutch housing 18. Those disc portions 28, 28a comprise brake friction material'and when assembled will lie with opposed surfaces 29 in contact as shown in FIG. 3, so as to form what may be considered a single brake disc that offers outer friction surfaces30, 30a. Further, due to the angularly staggered relation between the hub flanges 26, 26a, a side surface of each flange will engage a portion of the opposed cont-acting surface 29 on a respective disc portion 28 or 28a. It is conceivable, of course, that hub flanges may be designed to have rectangular, oval,

:or other outlines that have'a keying effect, and'therealong the axis of its mounting, as will be better understood as my description proceeds.

Referring again to FIG. 3, the portions 28 and 28a that form the brake disc will be embraced by brake plates 31, 32, those plates having clearance openings for the hub portions 23, 24. The brake plate 31 is formed to lie in surface contact with the end wall 14 of the hoist frame, as indicated at 33, and is formed with openings 34 that lugs 35 on end wall 14 will engage so that plate 31 cannot rotate on the hoist. Plate 31 may be formed on its periphery with a slotted portion 35 for coacting with a stud and pin arrangement 36 with which wall 14 can be equipped, should that be found helpful for holding the brake. and clutch construction in position while the hoistis being assembled. The

I believe it will be understood that the constant pressure of brake plates 31 and 32 relatively to brake disc 28, 28a on the shaft of motor M will enable the hoist to support aload at those times when the motor is not energized, and that the motor M will rotate the brake disc in slip friction relation to the plates while operating to lower a load. .When the motor operates in load lifting direction, the overrunning clutch 15 will free the hoist from the braking restraint, the operation being quite similar to that described in the Lytle application to which I have referred. i

, The brake disc 28, 28a naturally will operate under relatively little torque due to the effects of thegear reduction 11 between the hoist motor shaft 13 and the load shaft 12. Actually, the full gear reduction will not be essential to the effective operation of myinvention, it merely being necessary that theamount of torque applied to the brake disc be a fraction of the load shaft torque. Thus, my invention will operate well should the clutch and brake assembly 10 be mounted relatively to an operating shaft which is the shaft of an intermediate reduction gear, provided there be a wall of the hoist frame in contact with the assembly, and provided there remain a rather longer ratio of speed reduction between the operating shaft and the hoist load shaft.

' Therefore, l do not wish to be limited by a clutch and brake plate 31 is further formed on its periphery with finger portions 37 that are bent in axial direction to act as guides for the brake plate 32.

The brake plate 32 is formed on its periphery with portions 38 having openings adapted to slide on the guide fingers 37 of plate 31. Coil springs 39 act between the plate portions 38 and cotter pins 40 on guide fingers 37, pressing plates 31 and 32 toward one another and causing those plates to apply a constant frictional pressure against the opposed frictional surfaces 30, 30a of the brake disc that is formed by disc portions 28, 28a. 1

Further, the spring pressure of plates 31 and 32 will be effective to hold the disc portions 28, 28a in position assembled on the hub portions 23, 24, that being possible because the staggered hub flanges 26, 26a will locate that position of the disc portions, as I already have described.

The clutch and brake assembly 10, comprising the brake plates 31, 32, disc ,28, 28a, clutch 15 and their associated parts, can readily be installed as a unit on the hoist H so as to form a part of the hoist operating mechanism. That unit may be secured in position through the application of a snap-ring 41 to a groove on the end portion of motor shaft 13. As shown, a cover 42 may be applied to enclose the assembly 10.

brake assembly that is mounted relatively to a motor shaft. 1 I I To fully appreciate the. contribution of my present invention, it is necessary to realize-that a hoist load brake may be relatively small in size when it need not accept the full amount of the load shaft torque. However, such a brake will operate at relatively high speeds and may develop large amounts of heat due to slip friction when the brake is one that engages under constant pressure. In the construction that I have described, the heat that is. developed will be divided between the brake plates 31, 32, but at merely one surface of each plate while an opposed surface of plate 31 effectively dissipates heat through the hoist frame and a surface of r plate 32 is exposed to air. I have found that I amable thereby to build a hoist that is low in costyet enabling the temperature of the hoist to remain within an acceptable range, prolonging the life of the brake and hoist and greatly reducing a need for repair or adjustment.

I am aware that a circulation of air or other fluid has been found effective for cooling hoists in many cases but, so far as I know,no one working in the art has been U able prior to my invention to design a hoist'that will operate to the best advantage while having a brake that engages with constant frictional pressure. I believe, therefore, that my invention offers a contribution that will be of very considerable value to the hoist industry, and that the merits of my invention will be fully appreciated by persons who are skilled in the hoist art.

I claim: i

l. A hoist having a main frame on which a hoist motor is mounted, an operating shaft rotated by the motor and acting through speed reduction gearing to apply high torque to a rotatable load shaft, the operating shaft being reversible in operation whereby to lift and to lower a load on the load shaft, a pair of opposed brake plates mounted in aligned relation to the axis of said operating shaft and secured against rotating motion relatively to the hoist frame, one plate of said pair of opposed brake plates being directly mounted to the frame of the hoist and having an opening for accepting an end portionon the operating shaft, friction material forming a pairof brake discs assembled in position intermediate said brake plates, spring means pressing said pair of brake plates and causing each of those plates to apply constant braking pressure against a surface of said brake discs, an overrunning clutch assembly on said end portion of said shaft, including a clutch housing forming a first and second keying member mounted adjacent to each other but angularly offset from each other, said first and second keying members engaging key matching openings in said first and second brake discs respectively to provide contact between a portion of the adjacent surface of said first brake disc and said second keying member and between said second brake disc and said first keying member, a clutch part acting when said shaft rotates in load lowering direction to rotate said brake discs in slip friction relation to said pair of brake plates, and said one plate directly mounted to the frame of the hoist accepting a portion of the frictional energy that is due to the load lowering direction of said shaft being opposed by the effect of the constant braking pressure to dissipate the accepted portion of the frictional energy through the frame of the hoist.

2. The hoist construction as set forth in claim 1 wherein said first and second key members are a pair of adjacently mounted hexagonally shaped members angularly offset from each other and each of said brake discs being formed to have ahexagonally shaped opening allowing said brake discs to be fitted onto the first aligned relation to the'axis of said operating shaft and secured against rotating motion relatively to the hoist frame, one plate of said pair of opposed brake plates having an opening for accepting an end portion on the operating shaft, friction material'forming a brake disc assembled in position intermediate said brake plates, spring means pressing said pair of brake plates and causing each of those plates to apply constant braking pressure against a surface of said brake disc, an overrunning clutch on said end portion of said shaft, including a clutch part acting when said shaft rotates in load lowering direction to rotate said brake disc in slip friction relation to said pair of brake plates, each of those plates accepting a portion of the frictional energy that is due to the high speed of the operating shaft while opposed by the effect of the constant braking pressure, said overrunning clutch comprising a bushing keyed to said end portion of said operating shaft, and a clutch housing positioned in an opening in'said brake disc, said housing being equipped with means in keying relation to said opening in the brake disc, including a hub integrally mounted on the clutch housing and having formed on its periphery portions in keying relation to the opening in the brake disc, said brake disc including a plurality of disc portions assembled in contacting relation with the keying portions on the clutch housing engaging an opening in each disc portion and being formed in a staggered relation engaging also contacting surfaces of opposed disc portions for holding the brake disc in a predetermined axial position relatively to the clutch housing.

4. The hoist construction set forth in claim 3 in which said hoist frame comprises an end wall against which said one plate of said pair of brake plates lies in longitudinal surface contact, and including means engaging between said frame end wall, said one brake plate, and

the other of said brake plates to hold those plates 

1. A hoist having a main frame on which a hoist motor is mounted, an operating shaft rotated by the motor and acting through speed reduction gearing to apply high torque to a rotatable load shaft, the operating shaft being reversible in operation whereby to lift and to lower a load on the load shaft, a pair of opposed brake plates mounted in aligned relation to the axis of said operating shaft and secured against rotating motion relatively to the hoist frame, one plate of said pair of opposed brake plates being directly mounted to the frame of the hoist and having an opening for accepting an end portion on the operating shaft, friction material forming a pair of brake discs assembled in position intermediate said brake plates, spring means pressing said pair of brake plates and causing each of those plates to apply constant braking pressure against a surface of said brake discs, an overrunning clutch assembly on said end portion of said shaft, including a clutch housing forming a first and second keying member mounted adjacent to each other but angularly offset from each other, said first and second keying members Engaging key matching openings in said first and second brake discs respectively to provide contact between a portion of the adjacent surface of said first brake disc and said second keying member and between said second brake disc and said first keying member, a clutch part acting when said shaft rotates in load lowering direction to rotate said brake discs in slip friction relation to said pair of brake plates, and said one plate directly mounted to the frame of the hoist accepting a portion of the frictional energy that is due to the load lowering direction of said shaft being opposed by the effect of the constant braking pressure to dissipate the accepted portion of the frictional energy through the frame of the hoist.
 2. The hoist construction as set forth in claim 1 wherein said first and second key members are a pair of adjacently mounted hexagonally shaped members angularly offset from each other and each of said brake discs being formed to have a hexagonally shaped opening allowing said brake discs to be fitted onto the first and second hexagonally shaped members.
 3. In a hoist having a frame on which a hoist motor is mounted, an operating shaft rotated by the motor and acting through speed reduction gearing to apply high torque to a rotatable load shaft, the operating shaft being reversible in operation whereby to lift and to lower a load on the load shaft, the improvement that comprises a pair of opposed brake plates mounted in aligned relation to the axis of said operating shaft and secured against rotating motion relatively to the hoist frame, one plate of said pair of opposed brake plates having an opening for accepting an end portion on the operating shaft, friction material forming a brake disc assembled in position intermediate said brake plates, spring means pressing said pair of brake plates and causing each of those plates to apply constant braking pressure against a surface of said brake disc, an overrunning clutch on said end portion of said shaft, including a clutch part acting when said shaft rotates in load lowering direction to rotate said brake disc in slip friction relation to said pair of brake plates, each of those plates accepting a portion of the frictional energy that is due to the high speed of the operating shaft while opposed by the effect of the constant braking pressure, said overrunning clutch comprising a bushing keyed to said end portion of said operating shaft, and a clutch housing positioned in an opening in said brake disc, said housing being equipped with means in keying relation to said opening in the brake disc, including a hub integrally mounted on the clutch housing and having formed on its periphery portions in keying relation to the opening in the brake disc, said brake disc including a plurality of disc portions assembled in contacting relation with the keying portions on the clutch housing engaging an opening in each disc portion and being formed in a staggered relation engaging also contacting surfaces of opposed disc portions for holding the brake disc in a predetermined axial position relatively to the clutch housing.
 4. The hoist construction set forth in claim 3 in which said hoist frame comprises an end wall against which said one plate of said pair of brake plates lies in longitudinal surface contact, and including means engaging between said frame end wall, said one brake plate, and the other of said brake plates to hold those plates against rotating motion relatively to the hoist frame. 